This invention relates to a method for producing a planar type electron radiating device used for a flat panel display and, more particularly, to a flat type electron radiating device for radiating electrons from a plurality of pointed end cathodes.
As an image display device to take the place of the currently employed CRT for a television receiver, investigations are presently conducted into a planar type image display device. Such planar type image display device may be exemplified by a liquid crystal display, an electroluminescence device and a plasma display panel. A field emission type image display device is also attracting attention in respect of display luminosity on the viewing screen surface.
The field emission type image display device is now explained briefly. A number of conically-shaped cathodes of molybdenum etc. with a diameter of not more than 1.0 .mu.m, formed on a substrate by a semiconductor producing process, are used as radiation sources, and a plate-shaped gate electrode, provided with holes in register with the cathodes, are formed at the distal ends of the cathodes. The gate electrode is spaced apart from the distal ends of the cathodes and a high electrical voltage is applied across the gate electrode and the cathodes to produce field emission to extract an electron beam from the cathodes. This electron beam is irradiated on light emitting particles (phosphors) arranged on the back side of an anode to display a desired picture. Such field emission type image display device is described for example in U.S. Pat. No. 3,665,241, and the method for producing an electron radiating device, in which cathodes are formed on a substrate, is disclosed for example in JP Patent KOKOKU Publication No. 1-294336 (1989).
The known methods for producing an electron radiating device by arraying a plurality of pointed-end cathodes employed in the field emission type image display device suffer from a drawback that the cathodes tend to be detached from the substrate.
That is, with the known methods, an insulating film is formed on the substrate, and a gate electrode layer is formed in the insulating layer. The gate electrode layer and the insulating film are removed in regions thereof in which to form the cathodes, so that the major surface of the substrate is exposed at the bottom of the so-formed holes. A cathode electrode material is then deposited on the sidewall of the holes formed in the gate electrode layer by an oblique vacuum deposition technique to produce the pointed-end cathodes.
However, if ultrasonic cleaning is carried out for peeling off any excess cathode electrode material, the cathodes deposited on the major surface of the substrate are detached to render it difficult to radiate the electron beam.